Microfluidic devices have tremendous potential for applications in a variety of fields including drug discovery, biomedical testing, and chemical synthesis and analysis. In such devices, liquids and gases are manipulated in microchannels with cross-sectional dimensions on the order of tens to hundreds of micrometers. Processing in such microchannel devices offers a number of advantages including low reagent and analyte consumption, highly compact and portable systems, fast processing times, and the potential for disposable systems. However, in spite of all of their promise, microfluidic devices are currently being used in a limited number of applications and are in general still rather simple devices in terms of their operational complexity and capabilities. For example, in terms of making truly portable microanalytical systems, one of the current difficulties involves the simple integration of electronic (e.g., sensing methods) and fluidic elements into the same device. One of the most important issues, which controls this ability to integrate functions into the same device, and thus controls the level of functionality of a microfluidic device is, the method used to fabricate the structure. In addition, fluid microdynamics through the microchannels is important to avoid mixing in systems where mixing is not needed.
The two most prevalent methods for fabricating microfluidic devices to date involve either bonding together layers of ultraflat glass or elastomeric polymers such as poly(dimethylsiloxane). Both methods suffer from severe limitations and difficulties associated with integrating non-fluidic elements such as detectors with the microchannel system in the same substrate. Other methods suffer from several limitations including the fact that they require on the order of ten processing steps to complete the sequence for a single level of microchannels.